Delibr is a web based outliner for Product Managers who are working in Jira Cloud. 

Delibr is a document editor similar to Google docs (real time editing, collaboration etc.) but with two big differences for helping Product Managers:

1. Delibr is an outliner. This means that Delibr documents adhere to a tree structure and will not grow unwieldy to work in (even if they reach 20 pages). You can collapse and expand the tree structure when you're working in the document and when you're viewing it. 

2. Delibr offers a great Jira plugin. The plugin allows you to convert sections of your documents into Jira tickets. The Jira tickets will have a real time, two-way sync with the document. This saves time when creating tickets and removes the need to update across document and Jira tickets when something changes.

Note: you need a Delibr account in order to install this plugin. If you don't have a Delibr account yet you can start a free 14 day trial (no credit card needed) at www.delibr.com